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Writer's pictureEdward D. Andrews

How Many “Isaiahs”? A Question of Prophetic Authorship and Unity in the Book of Isaiah

The book of Isaiah stands as one of the most significant prophetic works within the Hebrew Scriptures, yet its authorship has been the subject of scholarly debate for centuries. Critics argue that the book was written by multiple authors, claiming that the prophecies of the exile and restoration in the latter chapters could not have been authored by Isaiah himself. These detractors suggest a "Deutero-Isaiah" or even a "Trito-Isaiah," leading to the notion of multiple contributors over different historical periods. However, this claim raises important questions for conservative biblical scholars who believe in the unity and divine inspiration of Scripture. How do we address these critical perspectives? Is there sufficient biblical and historical evidence to affirm the unity of Isaiah's authorship?



The Foundation of the Dispute: A Historical Overview of the Isaiah Authorship Question


It is essential to recognize that the debate over the authorship of Isaiah did not surface until many centuries after the book was composed. For over a millennium, the Jewish and Christian communities universally accepted Isaiah as the sole author of the entire book. The shift in opinion can be traced back to the 12th century C.E., when Jewish commentator Abraham Ibn Ezra first raised doubts about the unity of Isaiah. According to the Encyclopaedia Judaica, Ibn Ezra suggested that the latter portion of Isaiah (chapters 40-66) was the work of a prophet who lived during the Babylonian exile, not the 8th-century prophet Isaiah himself.


In the 18th century, this idea was further developed by German theologian Johann Christoph Döderlein, whose work promoted the notion that Isaiah’s prophecies concerning the Babylonian exile could not have been written before those events transpired. Since then, modern critical scholars have generally accepted that the book of Isaiah consists of multiple sources, assigning different authorship to various portions of the text. This view became widely adopted during the 19th and 20th centuries, and it is still held by many scholars today. The core argument of these scholars is that the latter chapters (40-66) reflect the historical context of the Babylonian exile and subsequent return to Jerusalem, a period long after Isaiah's death in the 8th century B.C.E. To these critics, such specificity about future events indicates that those chapters must have been written after the fact. But is this reasoning truly sound from a biblical perspective?



Prophecy and Divine Inspiration: Can the Future Be Known?


The critical perspective on Isaiah’s authorship challenges the very nature of biblical prophecy. Those who deny that Isaiah authored chapters 40-66 effectively argue that no one can accurately predict specific future events. This belief stems from a naturalistic worldview that excludes the possibility of divine inspiration. However, biblical prophecy, by its very nature, asserts that God can and does reveal future events to His prophets.


In Isaiah 46:9-10, Jehovah declares, “Remember the former things of old; for I am God, and there is none else; I am God, and there is none like me, declaring the end from the beginning, and from ancient times things that are not yet done, saying, My counsel shall stand, and I will do all my pleasure.” Here, we see the very essence of biblical prophecy: God, who exists outside of time, can declare events that have yet to occur with absolute certainty. The denial of Isaiah's authorship based on the specificity of future events not only undermines the credibility of Isaiah but also challenges the truthfulness of the entire biblical witness regarding prophecy.


The critics' reasoning does not stand up to the theological reality presented in Scripture. The God of the Bible is not constrained by time or human limitations. His ability to declare future events is consistent with His omniscience and sovereignty. As the apostle Peter reminds us, “For no prophecy was ever produced by the will of man, but men spoke from God as they were carried along by the Holy Spirit” (2 Peter 1:21, UASV). Therefore, we cannot dismiss the prophetic elements of Isaiah based on a humanistic view that denies divine intervention in history.



Evidence of Unity in the Book of Isaiah: A Close Look at Language and Themes


Critics argue that differences in style and subject matter between Isaiah 1-39 and Isaiah 40-66 suggest multiple authors. However, a closer examination of the text reveals remarkable consistency in language, themes, and theological emphasis, all of which point to a single author.


One of the most compelling pieces of evidence for the unity of Isaiah is the repeated use of the phrase “the Holy One of Israel.” This phrase appears twelve times in Isaiah 1-39 and thirteen times in Isaiah 40-66. Interestingly, outside of Isaiah, this term is found only six times in the rest of the Hebrew Scriptures. The frequent use of this unique description of Jehovah suggests a single, unified voice throughout the entire book of Isaiah.


Additionally, both sections of Isaiah contain similar figures of speech, such as the imagery of a woman in labor (Isaiah 26:17; 66:7) and the concept of a “way” or “highway” (Isaiah 11:16; 35:8). The prominence of Zion as a theological symbol also runs consistently throughout the book, appearing 29 times in chapters 1-39 and 18 times in chapters 40-66. This thematic continuity strongly supports the claim that Isaiah wrote the entire book.


The International Standard Bible Encyclopedia supports this view, noting that the individual style and unique expressions found throughout Isaiah make it difficult to argue for multiple authors. The idea that a single prophet, inspired by Jehovah, wrote the book in its entirety aligns with the evidence of unity within the text.


Testimony of the New Testament: How Did Jesus and the Apostles View Isaiah?


Perhaps the most compelling evidence for the single authorship of Isaiah comes from the New Testament. Jesus and the apostles consistently refer to Isaiah as the author of prophecies found in both the earlier and later portions of the book, demonstrating their belief in the unity of Isaiah.


In Luke 4:17-19, Jesus reads from the scroll of Isaiah in the synagogue, quoting what is now known as Isaiah 61:1-2. Luke explicitly states that “the scroll of the prophet Isaiah was handed to him.” There is no hint of any distinction between different “Isaiahs.” Jesus treats the entire book as the work of one prophet, and His acknowledgment carries divine authority. Additionally, Matthew 3:1-3 records how John the Baptist fulfilled the prophecy of Isaiah 40:3, attributing this prophecy to “Isaiah the prophet” without qualification.


The apostle Paul likewise refers to both early and late sections of Isaiah in his epistles, quoting Isaiah 53 and Isaiah 65 in Romans 10:16, 20 and Romans 15:12. Again, Paul makes no distinction between different authors. He simply refers to Isaiah as the prophet, affirming the unity of the text.


The inspired writers of the New Testament clearly accepted the unity of Isaiah’s authorship, treating the entire book as the work of one man. If Jesus and the apostles recognized Isaiah as the author of the entire text, should we not follow their example?



The Dead Sea Scrolls and Historical Evidence: Further Support for a Single Author


In addition to the internal evidence of Scripture, there is significant historical support for the unity of Isaiah’s authorship. The discovery of the Dead Sea Scrolls in the 20th century provided a treasure trove of ancient manuscripts, including a complete scroll of Isaiah dating to the second century B.C.E. This Isaiah Scroll, known as 1QIsaa, shows no indication of a division between Isaiah 39 and 40, which critics claim marks the beginning of Deutero-Isaiah. Instead, chapter 40 begins on the last line of a column, with no break or suggestion of a new author.


Furthermore, the Jewish historian Flavius Josephus, writing in the first century C.E., provides important testimony regarding the authorship of Isaiah. In Jewish Antiquities, Josephus recounts how the Persian king Cyrus became aware of Isaiah’s prophecies concerning him, which were written two centuries before Cyrus’ rise to power. Josephus writes, “These things Cyrus knew from reading the book of prophecy which Isaiah had left behind two hundred and ten years earlier.” According to Josephus, the prophecies of Isaiah were known and accepted as being written in the 8th century B.C.E., long before Cyrus came to power. This historical account further supports the traditional view of Isaiah’s authorship.



Prophecy Fulfilled: The Role of Babylon in Isaiah’s Writings


One of the central arguments of those who deny Isaiah’s authorship of chapters 40-66 is that Babylon is presented as the prevailing power in these chapters, even though Babylon did not rise to prominence until more than a century after Isaiah's time. However, this reasoning overlooks the nature of prophecy, which frequently speaks of future events as though they have already occurred. This technique emphasizes the certainty of prophetic fulfillment.


For example, in Isaiah 13:19, Babylon is described as “the most beautiful of kingdoms,” a prophecy concerning its future glory. Yet Babylon had not yet become the dominant world power at the time of Isaiah’s writing. Speaking of future events as though they have already happened is common in biblical prophecy. Isaiah’s prophecies about Babylon align with other examples in Scripture, such as Revelation 21:5-6, where the Apostle John describes future events with language indicating certainty.


The fact that Isaiah speaks of Babylon’s rise to power is not evidence of a later author but rather of the reliability and accuracy of biblical prophecy. As Jehovah declares in Isaiah 42:9, “Before they spring into being, I announce them to you.” This is the essence of true prophecy: the ability to declare future events with divine authority and certainty.


The evidence from Scripture, historical sources, and textual consistency all point to the unity of the book of Isaiah. Critics who deny Isaiah's authorship of chapters 40-66 fail to account for the nature of prophecy and the testimony of both the New Testament and historical records. The book of Isaiah remains a cohesive, divinely inspired work that testifies to the sovereignty of God over history and His ability to declare the end from the beginning.



About the Author

EDWARD D. ANDREWS (AS in Criminal Justice, BS in Religion, MA in Biblical Studies, and MDiv in Theology) is CEO and President of Christian Publishing House. He has authored over 220 books. In addition, Andrews is the Chief Translator of the Updated American Standard Version (UASV).


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